Not bad I am not gonna say it's more "refined" than Lion. It was a smooth transition so far. The transition was certainly better than SL to Lion, but that is to be expected. One thing that is great if things get to bad I can always run windows on this mac.

Upgraded on Sunday at home. Upgrade went smooth, I do seem to notice that the machine seems a bit quicker on load times of applications, though nothing clearly measurable. The better integration with iCloud is welcomed and the changes to Calendar and Address book are very welcome. Nothing earth shattering so far though.

A few apps bit the dust, one was an app to get rid of the monochrome finder icons and of course candybar is tossing in the towel.

To be honest the upgrade price seems my only irritation. Same price for SL or Lion users, seems Lion users should have had it for less since we paid to beta test for Apple. Not complaining about $19, but still

The upgrade went well, thanks for asking. I'm really liking ML so far. It feels more polished than Lion on a couple levels. So I would say that it's well worth the $19.99. That being said, I probably would have waited to upgrade a MacBook. There are some well known issues out there about a decrease in battery life._________________1.25GHz Mac Mini / 1.8GHz iMac G5 / 2.0GHz C2D Mac mini (2009)
4GB iPod mini / 2G iPod shuffle / 16GB iPhone 3G
Apple TV 2
iLife's a Bitch!

I had bought a MB Air 11 inch with Lion.
The battery didn't last forever or 8 hours
like Apple claimed. I really didn't expect
it to. When I installed Mountain Lion it
seems to last even less than Lion.

I kind of wish I had paid closer attention to
how long the battery lasts but in the long
run it really doesn't matter. We will always
be at the mercy of battery technology. I
make it a point to plug-in to A/C whenever
its possible.

I'm glad your upgrade went well. That seems
to be the norm. I don't like how locked down
OSX has gotten but I guess thats one of the
reasons why its relatively stable.

I agree with you, Mountain Lion feels very
polished and less than $20. Thats a no brainer.
BTW, the battery feels like its lasting about
half as long as before but I didn't track it
so its just my perception. Even with the
crap battery life I would do it (the Upgrade)
again._________________2011 Mac mini 2.7 GHz i7 with
16GB RAM, Samsung 512GB SSD
MacBook AIR 11 Inch
Mac mini, Model 1.1, 2.33 GHz C2D Proc
20" iMac G4 PPC

Bandit Bill, I get roughly 3.5 hours just surfing
Al Gores Interwebs. I do have the Display
turned almost ALL the way up. I suspect the
times given are for something like 50% power
set for the Display.

3.5 Hrs is a little low. I've seen people at our service desk say they were getting 2 hours, but when tested the MBA passed our battery diagnostic test.
I think they had a flaky router that was killing the battery when it had to renegotiate its connection.

I can't say 3.5 is the new 5 with ML. I haven't had any feedback, nor have I searched forums.

Hopefully you will get to 5 hours soon, if not You may want to consider getting the battery tested, prior to your warranty expiring. Our service department would do this for free. It only takes a couple minutes. A record is submitted to Apple's GSX (global service exchange) with the results.

You may want to get this done now and then again in a few months so that Apple has a track record of you having issues, otherwise if you get it tested just prior to warranty expiring and they don't find an issue, they may send you away for further testing and your warranty may expire.

It all went smooth for me at first. Now I get all kinds of bugs I mean crappy ones. Lion for me was better and I never liked that to begin with. I do like notifications, and messages. Doesn't matter if you got a ton of bugs. I thought message beta worked better than the public version. Mail is slow to open. I get flickering now and then on my monitor never seen that before then my computer just freezes. Then it will come back in about 5 minutes. It happens if I open a folder on the desktop. Sometimes I won't even have a cursor when I restart. Safari is slower ( actually everything is slower) but I like some of the features like sharing. I do like the newer features but just cant' stand dealing with a buggy system. I know some people got no problems with their spiffy new gear. I wish SL had messages. I really got used to that. I dont' know if I could go back just because of that one darn app. Dang you apple.